Reduced Friction Lubricating Oils Containing Functionalized Carbon Nanomaterials

ABSTRACT

Lubricating oil of reduced friction comprise lubricating oil base stock and dissolved therein carbon nanomaterials functionalized on their surface with ester or amide functionality and made using a technique involving multiple space apart in time or dropwise additions of reactants to the carbon nanomaterials.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Non-Provisional Application that claims priority to U.S.Provisional Application No. 61/271,109 filed Jul. 17, 2009, which isherein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to lubricating oils of reduced friction.

2. Description of the Related Art

Carbon nanotubes and fullerene materials are the subject of much currentinterest. Such materials are not soluble in aqueous, organic orhydrocarbon solvents so efforts have been made to functionalize them torender them soluble in one or more solvent categories.

U.S. Pat. No. 6,187,823 is directed to solubilizing single-walled carbonnanotubes by direct reaction with amines and alkylaryl amines having anuninterrupted carbon chain of at least 5 and preferably 9 carbon atomsin length. The single-walled carbon nanotubes are terminated withcarboxylic acid groups, then the carboxylic acid groups are reacted withan amine such as nonylamine or octadecylamine or an alkylaryl amine suchas 4-pentylaniline or 4-tetracontylaniline, in an appropriate solventsuch as toluene, chlorobenzene, dichlorobenzene, dimethylformamide (DMF)heramethylphosphoramide, dimethylsulfoxide (DMSO) with heating atbetween 50 to 200° C.

U.S. Published Application U.S. 2003/0065206 is directed toderivatization and solubilization of insoluble classes of carbonnanomaterials which include fullerenes, including very high molecularweight fullerenic materials generated in fullerenic soot, giantfullerenes, fullerenic polymers, carbon nanotubes and metal-carbonnanoencapsulates. The method involves cyclopropanation of the exteriorsurface of the fullerene or carbon nanotubes. The derivatives formed aredescribed as exhibiting increased solubility in solvents commonlyemployed, e.g., non-polar hydrocarbons and arene solvents. Thecyclopropanation reaction can be performed on fullerenes or carbonnanotubes, to the surfaces of which are devoid of any priorfunctionalization or on fullerenes or carbon nanotubes which have beenpreviously functionalized yet remain insoluble in solvents. The processinvolves the cyclopropanation reaction as previously applied to solublefullerenes by Bingel et al. which involves base-induced deprotination ofalpha halo substituted bis-malonates, see e.g. U.S. Pat. No. 5,739,376.The nucleophilic carbanion adds to the fullerene or carbon nanotubessurface, making a new carbon-carbon bond, followed by elimination of thehalide ion, completing the cyclopropanation and leaving a derivativegroup positioned 1, 2 across a carbon-carbon double bond of thefullerene or carbon nanotubes. The reaction is carried out in aheterogeneous mixture in a polar aprotic solvent, e.g. ether,tetrahydrofuran, 1,4-dioxane, dimethoxy-ethane or miscible mixturesthereof. The method is reported as being rapid, does not require heatingand does not require the use of strongly coordinating and reactive basessuch as amine DBU, but the use of sub-stoichiometric levels of solublebases such as nitrogen bases and DBU in the presence of an excessquantity of a proton scavenger is also disclosed.

Various cyclopropanation reagents are described, including:

wherein A is a carbon or silicon atom;

-   -   LG is the leaving group which includes —Cl, —Br, —I, —OSO₂R        where R is an optionally substituted alkyl or aryl group;    -   R₁ and R₂ are independently selected from the group consisting        of optionally-substituted alkyl, alkenyl, alkynyl or aryl        groups, —COOR₃ groups, —O—CO—R₃ groups, —COR₃ groups, —CO—NR₃R₄        groups, —O—CO—NR₃R₄ groups, —CN, —PO(OR₃)(OR₄) groups, and        —SO₂R₃ groups wherein R₃ and R₄ are independently selected from        hydrogen, an alkyl group, alkenyl group, alkynyl group or aryl        group, any one of which may be optionally further substituted.        Preferably R₁ and R₂ are both —COOR₃ groups.

At paragraph [0134] a sample of single-walled nanotubes was reactedunder modified Bingel-type conditions with diethylbromomalonate. It isstated that the derivatization protocol works on single-wallednanotubes, multi-walled nanotubes, nanotubes of varied diameter and bothnatural length and chemically-shortened nanotubes.

Derivatization renders the derivatized species soluble in commonnon-polar solvents. Solubility is defined as the dissolution of freemolecules (or salts) in the solvent with reversibility to remove thesolvent to recover the dissolved molecules or salts. Non-polar solventsare identified as including non-polar organic solvents such ashydrocarbons, and arenes and halogenated arenes, including toluene andbenzene.

U.S. Pat. No. 5,739,376 is directed to fullerene derivatives, methods ofpreparing derivatized fullerenes and methods of using derivatizedfullerenes. The fullerene is derivatized using materials of the formula:

wherein E¹ and E² are identical or different and are each COOH, COOR,CONRR′, CHO, COR, CN, P(O)(OR₂) and SO₂R where R and R′ are each astraight-chain or branched aliphatic radical (C₁ to C₂₀) which may beunsubstituted, monosubstituted or polysubstituted, and X is —Cl, —Br,—I, —OSR₂Ar, —OSO₂CF₃, —OSO₂C₄F₉.

The cyclopropanation reaction is carried out in a base such as alkalimetal hydride, alkali metal hydroxide, alkoxide, amide, amine, guanidineat from −78 to 180° C.

The final product can be made directly by using a material:

-   wherein E¹ and E² are already in their final desired form or    intermediate cyclopropanated fullerenes wherein E¹ and E² are esters    can be saponified to give E¹ to E² as corresponding acids, or    wherein E¹ and E² are alcohols which are reacted with an acid to    give esters of the desired carbon number.

U.S. Published Application U.S. 2006/0210466 is directed to theproduction of functionalized nanotubes using microwave radiation. Thenanotubes material is combined with the functionalizing reactant such asan acid, base, urea, alcohol, organic solvent, benzene, acetone or anyother reactant that achieves the desired functionalization reaction,then the mixture is subjected to appropriate microwave conditions toaffect the desired functionalization.

“Retention of Intrinsic Electronic Properties of Soluble Single-WalledCarbon Nanotubes after a Significant Degree of SidewallFunctionalization by the Bingel Reaction”, Tomohazu Umegama, et al., J.Phys. Chem. C 2007, 111, 9734-9741 reports single-walled carbonnanotubes functionalized at tips and defect sites with multiplealkyl-substituents and on sidewalls with phenyl-substituents to givesufficient solubility to the nanotube derivatives in organic solvents.Sidewall functionalization utilized the Bingel reaction. This articlealso reports the shortening of single-walled nanotubes using treatmentwith HCl and HNO₃ aqueous solutions, leaving shortened single-walledcarbon nanotubes with carboxylic groups at the upper ends (or tips) andat surface defect sites. These can be reacted with amine materials toyield amide functionalized single-walled carbon nanotubes exhibitingimproved dispersibility in common organic solvents such as chloroform,orthodichlorobenzene, tetrahydrofuran.

“Functionalization of Individual Ultra-Short Single-Walled CarbonNanotubes”, Jared M. Ashcroft, et al., Nanotechnology 17 (2006),5033-5037 reports the functionalization of 20-80 nm length single-walledcarbon nanotubes via in-situ Bingel cyclopropanation. The single-walledcarbon nanotubes are shortened via fluorination followed by pyrolysiswhich both shortens the nanotubes and creates sidewall defects throughwhich various agents can be internally loaded. The shortenedsingle-walled carbon nanotubes are functionalized via the Bingelreaction using a bromomalonate and sodium hydride (NaH) or theBingel-Hersch reaction using CBr₄ and DBU.

“Modification of Multi-Walled Carbon Nanotubes with Fatty Acids andTheir Tribological Properties as Lubricant Additives”, C. S. Chen, etal., Carbon 43 (2005), 1660-1666 teaches the treatment of multi-walledcarbon nanotubes with a mixture of sulfuric acid and nitric acid toproduce an oxidized material which was then boiled in HCl for two hours.The oxidized material was mechanically milled, then sonically mixed withstearic acid in deionized water to which was added sulfuric acid withadditionally refluxing at 100° C. for two hours. The reaction mixturewas cooled, then extracted with chloroform. Ball milled oxidizedmulti-walled carbon nanotubes and balled-milled stearic acid modifiedoxidized multi-walled carbon nanotubes were dispersed in pure liquidparaffin through sonication and stirring. Friction and wear tests wereperformed. The to liquid paraffin containing the stearic acid modifiedmulti-walled nanotubes presented lower friction coefficient and wearloss than did the pure liquid paraffin or the liquid paraffin-containingjust the ball milled oxidized multi-walled nanotubes. Wear loss andfriction coefficient decreased with increasing mass rates of stearicacid to oxidized multi-walled nanotubes up to a mass ratio of 2. Beyond2, the friction coefficient and wear loss increased.

“Functionalization of Single-Walled Carbon Nanotubes via the BingelReaction”, Karl S. Coleman, et al., J. Am. Chem. Soc. 2003, 125,8722-8723 teaches the cyclopropanation of single-walled carbonnanotubes. Single-walled carbon nanotubes were annealed under vacuum at1000° C. for three hours to remove any carboxylic acid groups present onthe surface. The decarboxylated single-walled carbon nanotubes weresuspended in dry orthodichlorobenzene (ODCB) to which was added diethylbromomalonate and 1,8-diazabicyclo[5.4.0]undecene (DBU). The mixture wasreacted with stirring for two hours and a modified single-wall nanotubesmaterial bearing >C(COO Et)₂ groups on the sidewall was isolated. Thismaterial was then either trans-esterified with 2-(methylthio) ethanol indiethyl ether and further contacted with a gold colloid to producefunctionalized single-walled carbon nanotubes with gold attached to thefunctional group, or the material was trans-esterified with the sodiumor lithium salt of 1H,1H,2H,2H-perfluoro decan-1-ol. These reactionsresulted in the introduction of chemical markers into the single-walledcarbon nanotubes to facilitate atomic force microscopy visualization and¹⁹F NMR and XPS spectroscopy for surface characterization.

DESCRIPTION OF THE INVENTION

The present invention is directed to a method for reducing the frictionof lubricating oils by the addition to the lubricating oil of containingfunctionalized carbon nanomaterials in an amount wherein thefunctionalized carbon nanomaterials are just soluble in the lubricatingoil and not dispersed solids.

Carbon nanostructure materials which are functionalized include, by wayof example and not limitation, nanohorns, fullerenes, nanoanions,single-wall carbon nanotubes, multi-walled carbon nanotubes andnonocomposites which may or may not have had their surfacesdecarboxylated. More particularly the functionalized carbonnanostructure materials are functionalized carbon nanotubes, preferablysingle-wall carbon nanotubes, more preferably short single-wall carbonnanotubes, and which have had their surfaces decarboxylated.

Fullerenes are cage-like carbon allotropes of the formula (_(C20+2m))(where m is an integer). They contain twelve five-membered rings andalso any number, but at least, two six-membered rings of carbon atoms.The most well known fullerene is the C60 fullerene, also commonlyidentified as “buckyball”.

Of the numerous carbon nanostructure materials, carbon nanotubes havebecome the most interesting.

Carbon nanotubes can be single-walled or multi-walled materials.

Multi-walled carbon nanotubes consist of concentrically nested tube-likegraphene structures with each successive concentric shell having alarger diameter than the next inner shell which it surrounds.Multi-walled carbon nanotubes can contain from two to multiple dozens ofconcentric tubes.

Single-walled carbon nanotubes, as the name implies, consist of a singletubular carbon graphene structure, i.e. a single layer of carbon atoms.Single-walled carbon nanotubes, therefore, ideally comprise a singlelayer of hexagonal carbon rings (a graphene sheet) that has rolled up toform a seamless cylinder. Incomplete rollup nanotubes may also resultsin holes (defects) in the nanotubes.

Such cylinders have diameters of anywhere from 0.05 to 2 micron,preferably 0.1 to 1 micron and lengths of many nanometers, even manycentimeters, for an extremely high length to diameter ratio.

Preferably the carbon nanostructure material which is functionalized inthe process of the present invention is a short single-walled carbonnanotube and which preferably has had its surface decarboxylated. Theinvention will be described hereinafter with reference to thenon-limiting example of short single-walled carbon nanotubes.

The functionalized short single-walled carbon nanotubes aresingle-walled carbon nanotubes between 1 to 10, preferably 1 to 0.5,microns in length and 0.01 to 50 nanometers in diameter and bear attheir edges and along the sidewall functional groups of the structure:

wherein R¹ and R² are the same or different and are selected fromhydrogen or C₁ to C₁₈ alkyl groups provided at least one of R¹ and R² isnot hydrogen, preferably R¹ and R² in total amount to at least 14carbons, y is 0 to 10, preferably 0 to 5, more preferably 1, Z is 0 or1, preferably 1, n and m are integers ranging from 0 to 2 provided n+mis at least 1, R³ is a C₁ to C₁₅ alkyl or C₆ to C₁₀ aryl group, R⁴ is aC₂ to C₁₄ alkyl group, C₆ to C₁₀ aryl, C₁ to C₁₀ alkylaryl or C₁ to C₁₀arylalkyl group, and x is an integer ranging from 0 to up to thereplaceable valance of the R³ group, preferably 1 to 3.

Short single-walled carbon nanotubes are secured either by starting withsingle-walled carbon nanotubes of the aforesaid length or,alternatively, long single-walled carbon nanotubes are shortened byoxidation using an aqueous solution of HNO₃ of 1 to 7 molar strength ora mixture of HCl and HNO₃ at a 3 to 1 volume ratio of concentrated HClto concentrated HNO₃ or 3 to 1 volume ratio of concentrated H₂SO₄ andHNO₃ producing single-walled carbon nanotubes of reduced length butcontaining carboxylic groups along the edges and at surface sidewalldefect sites. The short single-walled carbon nanotubes are subjected toannealing at high temperatures, to decarboxylate the short single-walledcarbon nanotubes. Procedures to shorten long single-walled carbonnanotubes are known in the art; see for example Bull. Korean Chem.Society 2004, Vol. 25, No. 9, 1301-1302 and for decarboxylating carbonnanotubes; see for example JACS 2003, 125, 8722-8723.

The carbon nanostructure material, preferably decarboxylated shortsingle-walled carbon nanotubes, are 100% carbon surface materialssubjected to [2+1] cyclopropanation using:

wherein R¹, R², R³, R⁴, y, m, n and x are as previously defined whereinthe carbon nanostructure material, preferably decarboxylatedshort-walled carbon nanotubes, is suspended in chlorinated benzene,preferably dry orthodichlorobenzene, and the materials of formula I orII and 1,8-diazabicyclo[5.4.0] undecene (DBU) are added to the suspendedcarbon nanostructure material in chlorinated benzene in multipleadditions over time or dropwise over time to yield the desiredfunctionalized carbon nanostructure material which is distinguished byhaving at least twice the level of substitution as compared tofunctionalized carbon nanostructure material made using the samematerials of formula I or II and the DBU as are added in the multipleadditions or dropwise but which are added all at once in a singleaddition, and even if the same total amount of such materials are addedall at once in a single addition as is added in total in the multipleadditions or dropwise. By multiple additions as used herein and in theappended claims is meant that the suspended carbon nanostructurematerial is mixed with quantities of materials of formula I or II andDBU at least twice, preferably at least three times, or more, over timewith intervals between each addition sufficient for reaction to occurbetween the suspended carbon nanostructure material and the material offormula I or II in the presence of the DBU, such interval being at leastsix hours, preferably six hours to four days, more preferably twelvehours to four days. Alternatively, materials of formula I or II and theDBU can be added to the carbon nanostructure material dropwise overtime, preferably over a period of at least two days, more preferablyover a period of at least four days, with stirring at a drop rate of onedrop every thirty seconds to thirty minutes, preferably one to tenminutes. The temperature is held at from 40 to 70° C., preferably 50 to60° C., during each addition of the multiple addition or during thedropwise addition and for one to four days, preferably three days,following the final addition step practiced by the practitioner, thechoice between dropwise addition and multiple additions and of thenumber of additions or the duration of the dropwise additions being leftto the discretion of the practitioner provided that if the multipleaddition procedure is adopted, there are at least two additions of thematerials of formula I or II in DBU to the carbon nanomaterial suspendedin the chlorinated benzene.

In another embodiment, the carbon nanostructure material, preferablyshort single-wall carbon nanotube material, more preferablydecarboxylated short single-wall carbon nanotube material, is suspendedin chlorinated benzene and materials of formula III:

wherein R⁵ and R⁶ are the same or different, preferably the same, andare selected from methyl, ethyl or propyl groups, preferably methylgroups, and DBU are added to the suspended carbon nanostructure materialin multiple additions over time or dropwise over time to yield anintermediate product of the formula:

The terms “multiple additions” and “dropwise” in this embodiment havethe same meaning as previously recited except in this instance it ismaterial III which is being added in the described manner. By so doing,the surface of the carbon nanostructure material, and in the case of theshortened single-walled carbon nanotubes, both the surface of the wallsand the tips at the end of the tubes, are substituted with the

in an amount at least twice the level of substitution obtained when thecarbon nanostructure material is reacted with material of formula IIIand the DBU in a single addition.

The material of formula IV is then subjected to trans-esterification ortrans-amidation using esterification or amidation agents of the type andformula which when reacted with the material of formula IV results inthe production of a functionalized carbon nanostructure material beingfunctional groups corresponding to the functional groups previouslyidentified as (a) or (b), the transesterification or amidation reactionbeing conducted at a temperature in the range of from 0 to 65° C. in anappropriate catalyst such as Group I alkali metal hydroxide in achlorobenzene solvent such as ODCB.

The amount of esterification or amidation agent used is an amountsufficient to fully esterify or amidate the material of formula IV. Byfully esterify or amidate is meant adding quantities of esterificationor amidation reactants sufficient so that upon spectroscopic analysis ofthe product the addition of more of such reactant does not result in anychange in the spectrum.

A wide range of lubricating base oils is known in the art. Lubricatingbase oils are both natural oils and synthetic oils. Natural andsynthetic oils (or mixtures thereof) can be used unrefined, refined, orrerefined (the latter is also known as reclaimed or reprocessed oil).Unrefined oils are those obtained directly from a natural or syntheticsource and used without added purification. These include shale oilobtained directly from retorting operations, petroleum oil obtaineddirectly from primary distillation, and ester oil obtained directly froman esterification process. Refined oils are similar to the oilsdiscussed for unrefined oils except refined oils are subjected to one ormore purification steps to improve at least one lubricating property.One skilled in the art is familiar with many purification processes.These processes include solvent extraction, secondary distillation, acidextraction, base extraction, filtration and percolation. Rerefined oilsare obtained by processes analogous to refined oils but using an oilthat has been previously used.

Groups I, II, III, IV and V are broad categories of base oil stocksdeveloped and defined by the American Petroleum Institute (APIPublication 1509, www.APL.org) to create guidelines for lubricant baseoils. Group I base stocks generally have a viscosity index of betweenabout 80 to 120 and contain greater than about 0.03% sulfur and/or lessthan about 90% saturates. Group II base stocks generally have aviscosity index of between about 80 to 120, and contain less than orequal to about 0.03% sulfur and greater than or equal to about 90%saturates. Group III stocks generally have a viscosity index greaterthan about 120 and contain less than or equal to about 0.03% sulfur andgreater than about 90% saturates. Group IV includes polyalphaolefins(PAO). Group V base stock includes base stocks not included in GroupsI-IV. The table below summarizes properties of each of these fivegroups.

Base Oil Properties Saturates Sulfur Viscosity Index Group I <90and/or >0.03% and ≧80 and <120 Group II >90 and ≦0.03% and ≧80 and <120Group III ≧90 and ≦0.03% and ≧120 Group IV Includes polyalphaolefins(PAO) and GTL products Group V All other base oil stocks not included inGroups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lardoil, for example), and mineral oils. Animal and vegetable oilspossessing favorable thermal oxidative stability can be used. Of thenatural oils, mineral oils are preferred. Mineral oils vary widely as totheir crude source; for example, as to whether they are paraffinic,naphthenic or mixed paraffinic-naphthenic. Oils derived from coal orshale are also useful. Natural oils vary also as to the method used fortheir production and purification; for example, their distillation rangeand whether they are straight run or cracked, hydrorefined, or solventextracted.

Group II and/or Group III hydroprocessed or hydrocracked base stocks,and synthetic oils such as polyalphaolefins, alkyl aromatics andsynthetic esters are well known base stock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oilssuch as polymerized and interpolymerized olefins (polybutenes,polypropylenes, propylene isobutylene copolymers, ethylene-olefincopolymers, and ethylene-alphaolefin copolymers, for example).Polyalphaolefin (PAO) oil base stocks are a commonly used synthetichydrocarbon oil. By way of example, PAOs derived from C₈, C₁₀, C₁₂, C₁₄olefins or mixtures thereof may be utilized. See U.S. Pat. Nos.4,956,122; 4,827,064; and 4,827,073, which are incorporated herein byreference in their entirety.

The hydrocarbyl aromatics can be used as base oil or base oil componentand can be any hydrocarbyl molecule that contains at least about 5% ofits weight derived from an aromatic moiety such as a benzenoid moiety ornaphthenoid moiety, or their derivatives. These hydrocarbyl aromaticsinclude alkyl benzenes, alkyl naphthenes, alkyl diphenyl oxides, alkylnaphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylatedthiodiphenol, and the like. The aromatics can be mono-alkylated,dialkylated, polyalkylated, and the like. The aromatics can be mono- orpoly-functionalized. The hydrocarbyl groups can also be comprised ofmixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups,cycloalkenyl groups and other related hydrocarbyl groups. Thehydrocarbyl groups can range from about C₆ up to about C_(o) with arange of about C₈ to about C₄₀ often being preferred. A mixture ofhydrocarbyl groups is often preferred. The hydrocarbyl group canoptionally contain sulfur, oxygen, and/or nitrogen containingsubstituents. The aromatic group can also be derived from natural(petroleum) sources, provided at least about 5% of the molecule iscomprised of an above-type aromatic moiety. Viscosities at 100° C. ofapproximately 3 cSt to about 50 cSt are preferred, with viscosities ofapproximately 3.4 cSt to about 20 cSt often being more preferred for thehydrocarbyl aromatic component. In one embodiment, an alkyl naphthalenewhere the alkyl group is primarily comprised of 1-hexadecene is used.Other alkylates of aromatics can be advantageously used. Naphthalene ormethyl naphthalene, for example, can be alkylated with olefins such asoctene, decene, dodecene, tetradecene or higher, mixtures of similarolefins, and the like. Useful concentrations of hydrocarbyl aromatic ina lubricant oil composition can be about 2% to about 25%, preferablyabout 4% to about 20%, and more preferably about 4% to about 15%,depending on the application.

Esters comprise a useful base stock. Additive solvency and sealcompatibility characteristics may be secured by the use of esters suchas the esters of dibasic acids with monoalkanols and the polyol estersof monocarboxylic acids. Esters of the former type include, for example,the esters of dicarboxylic acids such as phthalic acid, succinic acid,sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonicacid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety ofalcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol,2-ethylene alcohol, etc. Specific examples of these types of estersinclude dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexylfurmarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained byreacting one or more polyhydric alcohols, preferably the hinderedpolyols (such as the neopentyl polyols; e.g., neopentyl glycol,trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylolpropane, pentaerythritol and dipentaerythritol) with alkanoic acidscontaining at least about four carbon atoms, preferably C₅ to C₃₀ acidssuch as saturated straight chain fatty acids including caprylic acid,capric acids, lauric acid, myristic acid, palmitic acid, stearic acid,arachic acid, and behenic acid, or the corresponding branched chainfatty acids or unsaturated fatty acids such as oleic acid, or mixturesof any of these materials.

Suitable synthetic ester components include the esters of trimethylolpropane, trimethylol butane, trimethylol ethane, pentaerythritol and/ordipentaerythritol with one or more monocarboxylic acids containing fromabout 5 to about 10 carbon atoms. These esters are widely availablecommercially; for example, the Mobil P-41 and P-51 esters of ExxonMobilChemical Company.

Non-conventional or unconventional base stocks and/or base oils includeone or a mixture of base stock(s) and/or base oil(s) derived from: (1)one or more Gas-to-Liquids (GTL) materials, as well as; (2)hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed basestock(s) and/or base oil(s) derived from synthetic wax, natural wax orwaxy feeds, mineral and/or non-mineral oil waxy feed stocks such as gasoils, slack waxes (derived from the solvent dewaxing of natural oils,mineral oils or synthetic; e.g., Fischer-Tropsch feed stocks), naturalwaxes, and waxy stocks such as gas oils, waxy fuels hydrocrackerbottoms, waxy raffinate, hydrocrackate, thermal crackates, foots oil orother mineral, mineral oil, or even non-petroleum oil derived waxymaterials such as waxy materials received from coal liquefaction orshale oil, linear or branched hydrocarbyl compounds with carbon numberof about 20 or greater, preferably about 30 or greater and mixtures ofsuch base stocks and/or base oils.

GTL materials are materials that are derived via one or more synthesis,combination, transformation, rearrangement, and/ordegradation/deconstructive processes from gaseous carbon-containingcompounds, hydrogen-containing compounds and/or elements as feed stockssuch as hydrogen, carbon dioxide, carbon monoxide, water, methane,ethane, ethylene, acetylene, propane, propylene, propyne, butane,butylenes, and butynes. GTL base stocks and/or base oils are GTLmaterials of lubricating viscosity that are generally derived fromhydrocarbons; for example, waxy synthesized hydrocarbons, that arethemselves derived from simpler gaseous carbon-containing compounds,hydrogen-containing compounds and/or elements as feed stocks. GTL basestock(s) and/or base oils include oils boiling in the lube oil boilingrange (1) separated/fractionated from synthesized GTL materials such as,for example, by distillation and subsequently subjected to a final waxprocessing step which involves either or both of a catalytic dewaxingprocess, or a solvent dewaxing process, to produce lube oils ofreduced/low pour point; (2) synthesized wax isomerates, comprising, forexample, hydrodewaxed or hydroisomerized cat and/or solvent dewaxedsynthesized wax or waxy hydrocarbons; (3) hydrodewaxed orhydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T)material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possibleanalogous oxygenates); preferably hydrodewaxed orhydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxyhydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (orsolvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials,especially hydrodewaxed or hydroisomerized/followed by cat and/orsolvent dewaxed wax or waxy feed, preferably F-T material derived basestock(s) and/or base oil(s), are characterized typically as havingkinematic viscosities at 100° C. of from about 2 mm2/s to about 50 mm2/s(ASTM D445). They are further characterized typically as having pourpoints of −5° C. to about −40° C. or lower (ASTM D97). They are alsocharacterized typically as having viscosity indices of about 80 to about140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typicallyhighly paraffinic (>90% saturates), and may contain mixtures ofmonocycloparaffins and multicycloparaffins in combination withnon-cyclic isoparaffins. The ratio of the naphthenic (i.e.,cycloparaffin) content in such combinations varies with the catalyst andtemperature used. Further, GTL base stock(s) and/or base oil(s)typically have very low sulfur and nitrogen content, generallycontaining less than about 10 ppm, and more typically less than about 5ppm of each of these elements. The sulfur and nitrogen content of GTLbase stock(s) and/or base oil(s) obtained from F-T material, especiallyF-T wax, is essentially nil. In addition, the absence of phosphorus andaromatics make this material especially suitable for the formulation oflow SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stockand/or base oil is to be understood as embracing individual fractions ofsuch materials of wide viscosity range as recovered in the productionprocess, mixtures of two or more of such fractions, as well as mixturesof one or two or more low viscosity fractions with one, two or morehigher viscosity fractions to produce a blend wherein the blend exhibitsa target kinematic viscosity.

The functionalized carbon nanomaterials made according to the recitedprocess are dissolved in the lubricating oil base stock and/or base oil,the functionalized carbon nanomaterials being added to the lubricatingoil base stock or base oil, and the resulting mixture then beingsubjected to liquid/solid separation means such as filtration ofcentrifugation to remove any suspended functionalized carbonnanomaterial from the oil leaving only a lubricating oil containingfunctionalized carbon nanomaterial dissolved therein in an amount in therange 10 ppm to 10 wt %, preferably about 10 to 1000 ppm, morepreferably about 50 to 250 ppm.

The difference between solubility/dissolution and dispersion is a wellknown concept in chemistry and physics. Dispersion is the diffusion(suspension) of solid material in solvents without any chemical orphysical interaction with the solvent and the solid material may remainsuspended or become deposited or settle out over time.Solubility/dissolution of a material in a solvent occurs when thatmaterial's molecules and the solvent molecules exhibit intermolecularforces of attraction that holds these molecules together.

The lubricating oil of reduced friction comprising the lubricating oilbase stock/base oil and functionalized carbon nanomaterials dissolvedtherein made using the multiaddition or dropwise addition techniquewhich exhibits a higher degree of substitution than comparable materialsmade via the single addition technique recited in the prior art, mayfurther contain an additive amount of an organomolybdenum component,e.g. molybdenum dithiocarbamate (Moly DTC) or molybdenum dithiophosphate(Moly DTP) or other organic molybdenum compounds, including trinuclearmolybdenum DTC or DTP or an organomolybdenum-nitrogen complex component.Such organomolybdenum component or organomolybdenum-nitrogen complexcomponent can be present in the lubricating oil in an amount sufficientto contribute from about 10 to 600 ppm, preferably about 50 to 400 ppmmolybdenum to the lubricating oil.

Molybdenum dithiocarbamates (Moly DTC) are materials generally of theformula:

wherein R⁶ and R⁷ are independently a hydrocarbon group with 8 to 18carbon atoms and may or may not be the same, m and n are a positiveinteger provided that m+n−4.

Examples of the hydrocarbon group having 8 to 18 carbon atoms,represented by R⁶ and R⁷ in the general formula include hydrocarbongroups such as an alkyl group having 8 to 18 carbon atoms, an alkenylgroup having 8 to 18 carbon atoms, a cycloalkyl group having 8 to 18carbon atoms, an aryl group having 8 to 18 carbon atoms, an alkylarylgroup and an arylalkyl group. The above alkyl and alkenyl groups may belinear or branched. In the lubricating oil composition of the presentinvention, it is particularly preferable that the hydrocarbon grouprepresented by R⁶ and R⁷ have 8 carbon atoms.

Specific examples of the hydrocarbon group represented by R⁶ and R⁷include octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, octenyl,noneyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl,hexadecenyl, octadecenyl, dimethylcyclohexyl, ethylcyclohexyl,methylcyclohexylmethyl, cyclohexylethyl, propylcyclohexyl,butylcyclohexyl, heptylcyclohexyl, dimethylphenyl, methylbenzyl,phenethyl, naphthyl and dimethylnaphthyl groups.

Molybdenum dithiophosphates (Moly DTP) are materials generally of theformula:

wherein R⁸, R⁹, R¹⁰ and R¹¹ are the same or different hydrocarbyl groupscontaining 8 to 18 carbon atoms, X is oxygen or sulfur, preferably R⁸ toR¹¹ are C₈ to C₁₅ alkyl, alkenyl, cycloalkyl, aryl, alkylaryl, aralkyl,more preferably alkyl, most preferably C₈ to C₁₀ alkyl.

The term “organo molybdenum-nitrogen complexes” as used in the text andappended claims to define certain molybdenum complexes useful in thepresent invention embrace the organo molybdenum-nitrogen complexesdescribed in U.S. Pat. No. 4,889,647. The complexes are reactionproducts of a fatty oil, diethanolamine and a molybdenum source.Specific chemical structures have not been assigned to the complexes.U.S. Pat. No. 4,889,647 reports an infrared spectrum for a typicalreaction product of that invention; the spectrum identifies an estercarbonyl band at 1740 cm⁻¹ and an amide carbonyl band at 1620 μm⁻¹. Thefatty oils are glyceryl esters of higher fatty acids containing at least12 carbon atoms up to 22 carbon atoms or more. The molybdenum source isan oxygen-containing compound such as ammonium molybdates, molybdenumoxides and mixtures.

Other organo molybdenum complexes which can be used in the presentinvention are tri-nuclear and molybdenum-sulfur compounds described inEP 1 040 115 and WO 99/31113 and the molybdenum complexes described inU.S. Pat. No. 4,978,464.

The reduced friction lubricating oils containing the functionalizedcarbon nanomaterials may also contain additive amounts of otherlubricating oil performance enhancing additives such as detergents,dispersants, metal deactivators, pour point depressants, anti-oxidants,corrosion inhibitors, viscosity index improvers, viscosity modifiers,anti-wear/extreme pressure additives, soot compatibility agents,anti-foam agents, inhibitors, anti-rust additives, etc., all materialsalready well known in the art to the practitioner and documented in“Lubricants and Related Products” by Klamann, Verlag Chemie, DeerfieldBeach, Fla. ISBN 0-89573-177-0, “Lubricant Additives” by M. W. Ranney,Noges Data Corporation, Parkridge, N.J. (1978) and “LubricantAdditives”, C. V. Smallheer and R. K. Smith, Legiers Helen Company,Cleveland, Ohio (1967).

EXAMPLE

In the following example, the reactants were either acquired from acommercial source or prepared as follows:

A) Carbon nanotubes (CNTs) were obtained from Shenzhen Nanotech PortCo., Ltd. (L-SWNT, diameter <2 nm, length 5-15 μm, 50% SWCNT, 40% MWCNT,<5% amorphous carbon). The CNTs were oxidatively shortened and purifiedas well as thermally decarboxylated prior to being functionalized. (a)Shortening of CNT: Shortening of CNTs increase the solubility of suchmaterial. CNTs (1 g) were suspended in three M HNO_(3,aq) (50 mL),sonicated for 5 minutes at room temperature, and then refluxed for 60hours. The CNTs were filtered off (PTFE membrane filter, 0.45 μm) andwashed with deionized water to give shortened CNTs substituted at thetip and surface of this sidewall with carboxylic acid groups. Heating ofthe oxidized CNTs at 450° C. in a flow of dry N₂ for 3-4 hoursquantitatively removes all carboxylic acid groups. This procedureshortened/cut the carbon nanotube from 5-15 microns to 300-500nanometer. These shortened carbon nanotubes were characterized asfollows:

B) High Resolution Transmission Electron Microscopy (HR-TEM) wasperformed on a JEOL 2010F FEG TEM/STEM at 200 kV. Dilute solutions ofCNTs in THF were dropped onto a carbon-coated copper grid and thesolvent was allowed to evaporate. Thermal gravimetric analysis with massspectrometric detection of evolved gases was conducted on a MettlerToledo TGA SDTA 851e that was attached to a Pfeiffer Vacuum Thermostar™mass spectrometer (1-300 amu) via a thin glass capillary. Helium(99.99%) was used to purge the system to with a flow rate of 60 mL/min.Samples were held at 25° C. for 30 minutes before being heated to 1000°C. or 550° C. at rates of 2° C./min or 5° C./min. A mass range between14 m/z and 300 m/z was constantly scanned. UV-VIS spectra of solutionsin different solvents were recorded on a Varian Cary 50. FT-IRmeasurements were performed on a Bruker Vector 22. Powder X-RayDiffraction (XRD) measurements were run on a Bruker D8 Discoverdiffractometer equipped with a GADDS 2D-detector and operated at 40 kVand 40 mA. CuKal radiation (λ=1.54187 Å) was used and the initial beamdiameter was 0.5 mm. Spectra were evaluated in EVA and plotted withOrigin. Raman spectras were recorded on a Renshaw in Via RamanSpectroscopy instrument at an excitation wavelength of 633 nm and 50%power.

C) Malonate esters used to functionalize the short single-walled carbonnanotubes were either acquired from a commercial source and used withoutpurification or were synthesized as follows:

-   C-1—Synthesis of dihexadecyl malonate: H₂SO₄ (conc) (0.1 mL, 0.0036    mol % was slowly added to a mixture of dimethyl malonate (2 g, 0.015    mol) and hexadecanol (15 mL, 0.061 mol) and the mixture was heated    at reflux until all dimethyl malonate was converted according to TLC    (approximately 4 days). The product mixture was dissolved in    dichloromethane (DCM), extracted with water (3 times) and dried over    MgSO₄. An analytically pure sample was obtained by column    chromatography on silica gel using a 1:9 mixture of    ethylacetate/hexane. Yield: 5.5 g (65.7%), see JP 57067510.

C-2—Synthesis of 2-bromo dihexadecyl malonate: p-Toluene sulfonic acidmonohydrate (1.03 g, 0.0054 mol) and N-bromosuccinimide (0.64 g, 0.0035mol) were slowly added to a stirred solution of dihexadecyl malonate (2g, 0.0036 mol) in CH₃CN (20 mL). The resulting mixture was heated atreflux for 2 hours, evaporated and dissolved in dichloromethane. Theorganic layer was washed with H₂O, dried over MgSO₄, and concentrated.An analytically pure sample was obtained by column chromatography onsilica gel using a 1:4 mixture of ethylacetate/hexane. Yield: 1.8 g,78.9%.

See: Menger, F. M.; Johnston, D. E., Jr., Specific enzyme-induceddecapsulation. Journal of the American Chemical Society (1991), 113(14),5467-8.

C-3—Synthesis of bis(2-hexyldecyl malonate): H₂SO₄ (conc) (0.1 mL,0.0036 mol) was slowly added to a mixture of dimethyl malonate (3 g,0.022 mol) and 2-hexyl-1-decanol (19.7 mL, 0.068 mol) and the mixturewas heated at reflux until all dimethyl malonate was converted accordingto TLC (approximately 6 days). The product mixture was dissolved indichlormethane (DCM), extracted with water (3 times) and dried overMgSO₄. An analytically pure sample was obtained by column chromatographyon silica gel using a 1.5:8.5 mixture of ethylacetate/hexane. Yield: 8.1g (64.5%).

C-4—Synthesis of bis(2-hexyldecyl)-2-bromomalonate): p-Toluene sulfonicacid monohydrate (2.80 g, 0.014 mol) and N-bromosuccinimide (1.74 g,0.009 mol) were slowly added to a stirred solution of bis(2-hexadecylmalonate) (5.4 g, 0.009 mol) in CH₃CH (30 mL). The resulting mixture washeated at reflux for 2 hours, evaporated and dissolved indichloromethane. The organic layer was washed with H₂O, dried over MgSO₄and concentrated. An analytically pure sample was obtained by columnchromatography on silica gel using a 1:4 mixture of ethylacetate/hexane.Yield: 4.3 g (70.5%).

C-5—Synthesis of dimethyl-2-bromomalonate): p-Toluene sulfonic acidmonohydrate (11.0 g, 0.057 mol) and N-bromosuccinimide (1.74 g, 0.009mol) were slowly added to a stirred solution of dimethyl malonate (5.0g, 0.037 mol) in CH₃CH (30 mL). The resulting mixture was heated atreflux for 2 hours, evaporated and dissolved in dichloromethane. Theorganic layer was washed with H₂O, dried over MgSO₄ and concentrated. Ananalytically pure sample was to obtained by column chromatography onsilica gel using a 1:4 mixture of ethylacetate/hexane. Yield: 6.0 g(76.0%).

See: (1) Wolfe, Saul; Ro, Stephen; Kim, Chan-Kyung; Shi, Zheng, CanadianJournal of Chemistry (2001), 79(8), 1238-1258; (2) Matsumoto, Kiyoshi;Uchida, Takane; Yagi, Yoshiko; Tahara, Hiroshi; Acheson, R. Morrin,Heterocycles (1985), 23(8), 2041-3.

EXAMPLES

I. Preparation of CNT>C(COOC₁₆H₃₃)₂ (CNT-16): Shortened anddecarboxylated CNT compound (150 mg) was suspended in 50 mL of dryortho-dichlorobenzene (o-DCB) by sonication (5 minutes). 2-Bromodihexadecyl malonate (0.95 g, 1.5 mmol) and1,8-diazabicyclo[5.4.0]undecene (DBU) (0.45 g, 3.0 mmol) were added andthe mixture was allowed to react in a sonicator at 60° C. Three daysafter the initial batch of reactants was combined, additional amounts of2-bromo dihexadecyl malonate (0.95 g, 1.5 mmol) and1,8-diazabicyclo[5.4.0]undecene (DBU) (0.45 g, 3.0 mmol) were added withthe reaction being run for a total of 9 days. The reaction mixture wascooled to about 25° C. and filtered through a 0.45 μm PTFE filter. Asmall amount of CNT compound passed through this membrane filter and wascollected by twice filtering the filtrate through a 0.1 μm VCTP membranefilter. The filter residue was washed with ethanol until the filtratebecame clear to give 29 mg of CNT compound after drying in vacuum (<10⁻²mbar) for 6 hours. The first filter residue (0.45μ PTFE filter) wassuspended in ethanol and collected by centrifugation. This process wasrepeated 5 times to remove all organic contaminants. Finally, theobtained CNT compound was suspended in dichloromethane, sonication andheating was avoided, filtered off by passing the mixture through a 0.45μm filter and dried in vacuum (<10⁻² mbar) for 6 hours. Yield 95 mg. IR(KBi, cm⁻¹): 1740 (C=0), 2923 2959 (CH2). Raman (LL=633, P=50%, cm⁻¹):1334, 1587, 2625. Estimated number of ligands based on TGA is 1 per 22carbon atoms of CNT.

II. Preparation of CNT>CHCOOCH₂CH(C₆H₁₃)(C₈H₁₇)_(j) (CNT-6,10):Shortened and decarboxylated CNT compound (50 mg) was suspended in 20 mLof dry ortho-dichlorobenzene (o-DCB) by sonication (5 minutes).Bis(2-hexyldecyl) 2-bromomalonate (0.64 g, 1.0 mmol) and1,8-diazabicyclo[5.4.0]undecene (DBU) (0.31 g, 2.0 mmol) were added andthe mixture was allowed to react in a sonicator at 60° C. Additionalamounts of di(2-hexyldecyl) 2-bromomalonate (0.64 g, 1.0 mmol) and1,8-diazabicyclo[5.4.0]undecene (DBU) (0.31 g, 2.0 mmol) were addedafter 3 and 6 days of reaction with the reaction being run for a totalof 9 days. The reaction mixture was cooled to about 25° C. and filteredthrough a 0.45 μm PTFE filter. A small amount of CNT compound passedthrough this membrane filter. The filter residue was washed with ethanoluntil the filtrate became clear to give 7 mg of CNT compound afterdrying in vacuum (<10⁻² mbar) for 6 hours.

The first filter residue (0.45 μm PTFE filter) was suspended in ethanoland collected by centrifugation. This process was repeated 5 times toremove all organic contaminants. Finally, the obtained CNT compound wassuspended in DCM, sonication and heating was avoided, filtered off bypassing the mixture through a 0.45 μm filter and dried in vacuum (<10⁻²mbar) for 6 hours. Yield: 63 mg. IR (KBr, cm⁻¹): 1744 (C=0), 2920, 2850(CH2). Raman (LL=633, P=50%, cm⁻¹): 1330, 1591, 2617. Estimated numberof ligands based on TGA is 1 per 480 C-atoms of CNT.

III. Synthesis of CNT>C[CONH-Ph(OC₁₂)₃]₂ (CNT-NPhC₁₂): Shortened anddecarboxylated CNT compound (80 mg) was suspended in 20 mL of dryortho-dichlorobenzene (o-DCB) by sonication (5 minutes).Dimethyl-2-bromomalonate (0.32 g, 1.5 mmol) and 1,8-diazabicyclo[5.4.0]undecene (DBU) (0.46 g, 3.0 mmole) were added and the mixture wasallowed to react in a sonicator at 60° C. Additional amounts ofdimethyl-2-bromomalonate (0.32 g, 1.5 mmol) and 1,8-diazabicyclo[5.4.0]undecene (DBU) (0.46 g, 3.0 mmol) were added after 3 days of the 5 dayreaction period. At the end of this period,3,4,5-tris(dodecyloxy)aniline (2.6 g, 4 mmol) was gradually added to thereaction mixture over 5 days and the mixture was sonicated at 60° C. foranother 5 days. The reaction mixture was cooled to 25° C. and filteredthrough a 0.46 μm PTFE filter. No CNT compound passed through thismembrane filter because larger aggregates than for the previous CNTcompounds were formed. The filter residue was suspended in ethanol andcollected by centrifugation. This process was repeated 5 times to removeall organic contaminants. Finally, the obtained CNT compound wassuspended in DCM, sonication and heating was avoided, filtered off bypassing the mixture through a 0.45 μm filter and dried in a vacuum(<10⁻² mbar) for 6 hours. Yield: 131 mg. IR (KBr, cm⁻¹): 1745 (CONH,2921, 2851 (CH₂), 3441 (NH). Raman (LL=633, P=50%, cm⁻¹): 1334, 1590,2631. Estimated number of ligands based on TGA is 1 per 900 C-atoms ofCNT.

The solubilities of the CNT-16 and CNT-6,10 materials in differentsolvents was investigated. Solubility is difficult to define for CNTmaterials because of their large size and strong van-de-Waalsinteractions (aggregation). All solubility measurements reported hereare based on UV/VIS adsorption measurements of saturated solutions basedon a calibration curve obtained in toluene solution.

For comparison purposes two additional batches of CNT-6,10 materialswere made but not employing the multiple addition technique outlined inExample II.

In Comparison I the shortened and decarboxylated CNT compound (50 mg)was suspended in 200 ml of dry orthodichlorobenzene (o-DCB) bysonication (5 minutes). Bis-(2 hexyldecyl) 2-bromomalonate (0.64 g, 1.0mmol) and 1,8-diazabicyclo[5.4.0]undecene (DBU) (0.31 g, 2.0 mmol) wereadded once and the mixture was allowed to react in a sonicator at 60° C.for 4 days.

In Comparison II the shortened and decarboxylated CNT compound (50 mg)was suspended in 20 ml of dry ortho-dichlorobenzene (o-DCB) bysonication (5 minutes). Bis-(2 hexyldecyl) 2-bromomalonate (1.28 g, 2mmol) and 1,8-diazabicyclo [5.4.0] undecene (DBU) (0.62 g, 4.0 mmol)were added once and the mixture was allowed to react in a sonicator 60°C. for 4 days.

In both Comparison I and Comparison II, the product purificationtechnique recited in Example II was employed.

Absorbance values (at a recited wavelength) of CNTs in differentsolvents at room temperature after centrifugation to remove suspendedsolids is reported in Table 1. The values in parentheses are thecalculated concentration of the solutions in mg of CNT/dm³ of solvent.

In regard to CNT-NPhC₁₂, excess CNT-NPhC₁₂ was suspended and dissolvedin DCM by sonication at 45° C. for 30 minutes. The absorption of thissolution/suspension was monitored for 4 days and a constant value wasobtained after 1 day (55% of the original absorption obtained 5 minutesafter sonication). Centrifugation (1200 g) of a freshly sonicatedsolution for 20 minutes resulted in the same absorption as a solutionthat settled for 1 day while filtration of a freshly sonicated solutionthrough a 0.45 micron filter gave a 10% larger absorbance value.Identical results were obtained in toluene solution. In Table 1 belowthe absorbance reported is for the freshly sonicated/centrifugedmaterial.

These molecules have different extinct coefficients, and thereforeabsorb and emit light with different energies depending on theirstructures. Calculated concentration in this case was arrived at bymeasuring the absorption at the appropriate wave length, determining theextinction coefficient from the spectra, and then plot it against thereference graph. It is a standard procedure known as the Beer-Lambertlaw which relates the absorbance of UV/Vis light, the concentration ofthe sample, the length of the light path, and the molar absorptivity.

TABLE 1 CNT-6,10 CNT-6,10 CNT-NPhC₁₂ CNT-16 (Example CNT-6,10 Comparison(Example Solvent (Example I) II) Comparison I II III) THF (350 nm) 0.7870.381 (40.36) (19.54) CHCl₃ (350 nm) 1.585 1.212 0.634 0.630 1.7363(81.28) (62.15) (29.72) (29.58) (89.03) DCM (350 nm) n.a. n.a. Toluene(350 nm) 0.346 0.516 (17.74) (26.46) Hexane (350 nm) 0.043 0.110 0.2553(2.21) (5.64) (15.68) Special Oil (400 nm) 0.098 0.158 0.8725 (5.76)(9.29) (8.80) 5W-30 (400 nm) 0.866 0.349 0.9300 (50.94) (20.53) (7.88)

Solubility of the CNT precursor, the decarboxylate short single-walledcarbon nanotube before the functionalization reaction, in chloroform is1.07 mg/dm³. Consequently, the functionalization reaction increasedtheir solubility by a factor of up to 89 as read directly from thecalibration curve or by a factor of 76 based on direct calibration frompeak intensity.

As can be seen by considering CNT-6,10 product of Example II versus theCNT-6,10 product of Comparison 1 and Comparison H, functionalizationemploying a single addition step (Comparison I) and regardless ofwhether it employs in that single addition step a double amount ofreactant (Comparison II), the products exhibit an adsorption of 0.634and 0.630, respectively, while CNT-6,10 made using multiple additions ofthe malonate/DBU reactants exhibits an adsorption of 1.212, double thevalue, indicative of an at least doubling of the to level ofsubstitution achieved by the multiple addition process versus the singleaddition process exemplary of the techniques used in the prior art.

High Frequency Rig Studies

Functionalized CNT showed reduced friction in GTL and formulated oilrelative to Moly trimer, especially at high temperature of the testprocedure.

The HFRR is a standard high frequency friction rig test ASTM (D6079).HFRR conditions used: 2° C./minute for 75 minutes, temperature range 30to 180° C.

Nanotube Friction Modifiers

0W40 Max. GTL + 0W40 Max 0W40 Max. Visom¹ w/o Time, GTL + 0.2 wt 100 ppmVisom with Visom w/o Moly + 100 ppm min GTL % Moly CNT-NPhC₁₂ Moly MolyCNT-NPhC₁₂ Friction 0 0.081 0.074 0.064 0.072 0.082 0.074 20 0.090 0.0850.082 0.083 0.086 0.082* 40 0.079 0.051 0.085 0.079 0.085 0.081* 600.114 0.042 0.050 0.069 0.115 0.050 80 0.120 0.044 0.050 0.044 0.1240.050 100 0.120 0.057 0.050 0.050 0.123 0.046 120 0.120 0.068 0.0380.061 0.127 0.038 135 0.120 0.072 0.034 0.069 0.129 0.031 *The valuereported is likely a tribological effect. It is also so small that it iswithin the experimental error of this instrument. ¹A lubricating oilbase stock made by hydroisomerizing a slack wax secured from a petroleumsource.

As can be seen, the presence of a solution amount of as little as 100ppm CNT-NPhC₁₂ in the lubricating oil (GTL or a Visom-based 0W40 oil(absent moly) resulted in the long term reduction of friction ascompared to GTL per se or GTL containing as much as 0.2 wt % molydenum,as well as compared to a Visom-based 0W40 oil with or without moly. Thedata beginning at 100 minutes is the most significant showing that athigh temperature (180° C.) and for the long term for lubricating oilscontaining very low levels of the functionalized carbon nanostructurematerials, low concentrations of such materials dissolved in thelubricating oil as compared to being suspended or dispersed in thelubricating oil, the friction is reduced to a level about four timeslower than for the oil alone and at least about two times lower than forthe oil containing a conventional friction modifier. This frictionreduction at higher temperatures and for an extended period of time isessential for fuel economy retention.

1. A method for reducing the friction of a lubricating oil comprising abase stock or base oil by dissolving in the base stock or base oil from10 ppm to 10 wt % of a functionalized carbon nanostructure materialwhich functionalized carbon nanostructure material is made by a processcomprising: (1) suspending a carbon nanostructure material in achlorinated benzene solvent; and (2) adding to the suspension of (1), inmultiple additions over time, materials of the formula:

wherein R¹ and R² are the same or different hydrogen or C₁ to C₁₈ alkylgroups provided at least one of R¹ and R² is not hydrogen, y is 0 to 10,Z is 0 or 1, n and m are integers ranging from 0 to 2 provided n+m is atleast 1, R³ is a C₁ to C₁₅ alkyl or C₆ to C₁₀ aryl group, R⁴ is a C₂ toC₁₄ alkyl group, C₆ to C₁₀ aryl, C₁ to C₁₀ alkylaryl or C₁ to C₁₀arylalkyl group, and x is an integer ranging from 0 to up to thereplaceable valence of the R³ group, and 1,8-diazabicyclo[5.4.0]undecene (DBU), wherein the resulting functionalized carbonnanostructure material has at least twice the level of functionalizationas compared to functionalized carbon nanostructure material made usingthe same carbon nanostructure material and material of formula I or IIand DBU when the materials of formula I or II and DBU are added to thecarbon nanostructure material all at once in a single addition.
 2. Amethod for reducing the friction of a lubricating oil comprising a basestock or base oil by dissolving in the base stock or base oil from 10ppm to 10 wt % of a functionalized carbon nanostructure material whichfunctionalized carbon nanostructure material is made by a processcomprising: (1) suspending a carbon nanostructure material in achlorinated benzene solvent; and (2) adding to the suspension of (1),dropwise over time, material of the formula:

wherein R¹ and R² are the same or different hydrogen or C₁ to C₁₈ alkylgroups provided at least one of R¹ and R² is not hydrogen, y is 0 to 10,Z is 0 or 1, n and m are integers ranging from 0 to 2 provided n+m is atleast 1, R³ is a C₁ to C₁₅ alkyl or C₆ to C₁₀ aryl group, R⁴ is a C₂ toC₁₄ alkyl group, C₆ to C₁₀ aryl, C₁ to C₁₀ alkylaryl or C₁ to C₁₀arylalkyl group, and x is an integer ranging from 0 to up to thereplaceable valence of the R³ group, and 1,8-diazabicyclo[5.4.0]undecene (DBU), wherein the resulting functionalized carbonnanostructure material has at least twice the level of functionalizationas compared to functionalized carbon nanostructure material made usingthe same carbon nanostructure material and material of formula I or IIand DBU when the materials of formula I or II and DBU are added to thecarbon nanostructure material all at once in a single addition.
 3. Amethod of reducing the friction of a lubricating oil comprising a basestock or base oil by dissolving in the base stock or base oil from 10ppm to 10 wt % of a functionalized carbon nanostructure material whichfunctionalized carbon nanostructure material is made by a processcomprising: (1) suspending a carbon nanostructure material in achlorinated benzene solvent; (2) adding of the suspension of (1), inmultiple additions over time, material of the formula:

wherein R⁵ and R⁶ are the same or different and are selected frommethyl, ethyl or propyl groups and DBU to yield a product of theformula:

and (3) trans-esterifying or trans-amidating material of formula IV withan esterification or amidation agent of the type which when reacted withthe material of formula IV results in the production of a functionalizedcarbon nanostructure material of the formula:

wherein R¹ and R² are the same or different hydrogen or C₁ to C₁₈ alkylgroups provided at least one of R¹ and R² is not hydrogen, y is 0 to 10,preferably 0 to 5 and Z is 0 or 1, n and m are integers ranging from 0to 2 provided n+m is at least 1, R³ is a C₁ to C₁₅ alkyl or C₆ to C₁₀aryl group, R⁴ is a C₂ to C₁₄ alkyl group, C₆ to C₁₀ aryl, C₁ to C₁₀alkylaryl or C₁ to C₁₀ arylalkyl group, and x is an integer ranging from0 to up to the replaceable valence of the R³ group, wherein theresulting functionalized carbon nanostructure material has at leasttwice the level of functionalization as compared to functionalizedcarbon nanostructure material made using the same carbon nanostructurematerial and material of formula III and DBU when the materials offormula III and DBU are added to the carbon nanostructure material allat once in a single addition.
 4. A method for reducing the friction of alubricating oil comprising a base stock or base oil by dissolving in thebase stock or base oil from 10 ppm to 10 wt % of a functionalized carbonnanostructure material which functionalized carbon nanostructurematerial is made by a process comprising: (1) suspending a carbonnanostructure material in a chlorinated benzene solvent; (2) adding tothe suspension of (1), dropwise over time, material of the formula:

wherein R⁵ and R⁶ are the same or different and are selected frommethyl, ethyl or propyl groups, and 1,8-diazabicyclo[5.4.0]undecene(DBU) to yield a product of the formula:

and (3) trans-esterifying or trans-amidating the material of formula IVwith an esterification or amidation agent of the type which when reactedwith the material of formula IV results in the production of afunctionalized carbon nanostructure material of the formula:

wherein R¹ and R² are the same or different hydrogen or C₁ to C₁₈ alkylgroups provided at least one of R¹ and R² is not hydrogen, y is 0 to 10,preferably 0 to 5 and Z is 0 or 1, n and m are integers ranging from 0to 2 provided n+m is at least 1, R³ is a C₁ to C₁₅ alkyl or C₆ to C₁₀aryl group, R⁴ is a C₂ to C₁₄ alkyl group, C₆ to C₁₀ aryl, C₁ to C₁₀alkylaryl or C₁ to C₁₀ arylalkyl group, and x is an integer ranging from0 to up to the replaceable valence of the R³ group, wherein theresulting functionalized carbon nanostructure material has at leasttwice the level of functionalization as compared to functionalizedcarbon nanostructure material made using the same carbon nanostructurematerial and material of formula III and DBU when the materials offormula III and DBU are added to the carbon nanostructure material allat once in a single addition.
 5. The method of claim 1 wherein thecarbon nanostructure material is single-walled carbon nanotubes.
 6. Themethod of claim 5 wherein the single-walled carbon nanotubes are shortsingle-walled nanotubes having a length between 1 to 10 microns and adiameter between 0.01 to 50 nanometers.
 7. The method of claim 2 whereinthe carbon nanostructure material is single-walled carbon nanotubes. 8.The method of claim 7 wherein the single-walled carbon nanotubes areshort single-walled carbon nanotubes having a length between 1 to 10microns and a diameter between 0.01 to 50 nanometers.
 9. The method ofclaim 3 wherein the carbon nanostructure material is single-walledcarbon nanotubes.
 10. The method of claim 9 wherein the single-walledcarbon nanotubes are short single-walled carbon nanotubes having alength between 1 to 10 microns and a diameter between 0.01 to 50nanometers.
 11. The method of claim 4 wherein the carbon nanostructurematerial is single-walled carbon nanotubes.
 12. The method of claim 11wherein the single-walled carbon nanotubes are short single-walledcarbon nanotubes having a length between 1 to 10 microns and a diameterbetween 0.01 to 50 nanometers.
 13. The method of claim 1, 5 or 6 whereinthe carbon nanostructure material has had its surface decarboxylated.14. The method of claim 2, 7 or 8 wherein the carbon nanostructurematerial has had its surface decarboxylated.
 15. The method of claim 3,9 or 10 wherein the carbon nanostructure material has had its surfacedecarboxylated.
 16. The method of claim 4, 11 or 12 wherein the carbonnanostructure material has had its surface decarboxylated.
 17. Themethod of claim 1 wherein the suspended carbon nanostructure material ismixed with quantities of materials of formula I or II and DBU at leasttwice with interval between the additions sufficient for reaction tooccur between the suspended carbon nanostructure material and thematerial of formula I or II and DBU.
 18. The method of claim 17 whereinthe interval between additions is at least six hours.
 19. The method ofclaim 2 wherein the addition of material of formula I or II and DBU tothe suspended carbon nanostructure material dropwise over a period of atleast two days at a rate of one drop every thirty seconds to thirtyminutes.
 20. The method of claim 3 wherein the suspended carbonnanostructure material is mixed with quantities of material of formulaIII and DBU at least twice with interval between the additionssufficient for reaction to occur between the suspended carbonnanostructure material and the material of formula III and DBU.
 21. Themethod of claim 20 wherein the interval between additions is at leastsix hours.
 22. The method of claim 4 wherein the addition of material offormula III and DBU to the suspended carbon nanostructure material isdropwise over a period of at least two days at a rate of one drop everythirty seconds to thirty minutes.
 23. The method of claim 1, 2, 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 17, 18, 19, 20, 21 or 22 wherein the temperatureis held at from 40 to 70° C. during the addition step and for one tofour days following the final addition of the material to the suspendedcarbon nanostructure materials.
 24. The method of claim 1, 2, 3 or 4wherein the lubricating oil further contains an additive amount of anorganomolybdenum compound.